#define _CRT_SECURE_NO_WARNINGS 1


#include<stdio.h>

int fun(int n)
{
	int count = 0;
	while (n > 0)
	{
		count++;
		n -= 70;
	}
	return count;
}
int main()
{
	int temp = 0, n = 0, i = 0, count = 0;
	scanf("%d", &n);
	for (i = 0; i < n; i++)
	{
		scanf("%d", &temp);
		count += fun(i);
	}
	printf("%.1lf\n", count * 0.1);

	return 0;
}